The sensor element encompasses in particular at least one electrical, electrochemical, and/or electronic functional element in a first end region, as a rule facing toward the exhaust gas, of the sensor element. A capability for supplying electricity to the sensor element is provided in the present case by a contact surface on the outer surface of the sensor element in a second region, as a rule facing away from the exhaust gas.
In addition to electrical conductivity, the contact surface is required to have high temperature resistance and chemical resistance during operation and during manufacture of the sensor element. Noble metals, for example platinum and the like, are therefore commonly used. Because such noble metals are comparatively expensive, it is generally desirable to reduce the size of the contact surface as much as possible.
On the other hand, making the contact surface smaller is to be regarded as critical if contacting can no longer be reliably ensured under all circumstances as a result of production tolerances of the sensor element or as a result of production tolerances of contact elements interacting with the sensor element in a sensor, for example metal wires, pins, springs, or the like.
Sensor elements having contact surfaces are already believed to be understood from DE 102 08 533 A1, DE 10 2004 047 783 A1, and DE 10 2009 055 416 A1. These contact surfaces are embodied rectangularly in their end regions facing away from the functional elements.